1. Field
The present invention relates to a printed wiring board and an electric tool switch provided therewith.
2. Related Art
In order to mount or attach various components, a soldering land is provided in a printed wiring board while exposed on a front face of the printed wiring board. Particularly, the printed wiring board used in an electric tool switch is connected to a constituent member (for example, casing member formed by sheet metal working) constituting the electric tool switch by soldering. FIG. 5 is a perspective view schematically illustrating a connection portion between printed wiring board 110 and constituent member 120 in the electric tool switch. As illustrated in FIG. 5, projecting portion 121 is provided in constituent member 120. Hole 111 in which projecting portion 121 is inserted is made in printed wiring board 110. Soldering land 112 to which projecting portion 121 is soldered is provided on a front face of printed wiring board 110 so as to surround hole 111. Soldering land 112 is a film made of metal. In the electric tool switch, a contact mechanism that turns on and off a switch is arranged on a side opposite to the soldering front face of printed wiring board 110.
FIGS. 6A and 6B are sectional views illustrating a configuration of a conventional soldering land, in which FIG. 6A illustrates a configuration of a through-hole land, and FIG. 6B illustrates a configuration of a single-sided land.
As illustrated in FIG. 6A, a metallic film constituting through-hole land 112A extends from front face 110a of printed wiring board 110 to back face 110b of printed wiring board 110 through a sidewall constituting hole 111. On the other hand, a metallic film constituting single-sided land 112B is formed only on front face 110a of printed wiring board 110.
Japanese Unexamined Patent Publication No. 2012-94681 discloses a technology in which an end portion of the land is held by a paint printed by silkscreen in order to prevent the metallic film constituting the land from peeling from the printed wiring board.
In the electric tool switch including the configuration in FIG. 5, a vibration is transmitted to the connection portion between printed wiring board 110 and constituent member 120 during switch operation. Therefore, it is necessary for the connection portion between printed wiring board 110 and constituent member 120 to secure a strength to a degree that a wiring pattern of printed wiring board 110 does not peel against the vibration. Similarly, in soldering projecting portion 121, it is necessary to prevent a flux generated by the soldering from extending onto a back face side of the printed wiring board. A conduction failure is generated when the flux generated by the soldering adheres to the contact mechanism provided on the side opposite to the soldering front face of printed wiring board 110.
However, in the configuration of the conventional land in FIGS. 6A and 6B, it is difficult to satisfy both the securement of the peeling strength against the vibration in the wiring pattern of the printed wiring board and the prevention of the flux from extending onto the back face side of the printed wiring board.
In the configuration of through-hole land 112A in FIG. 6A, the peeling strength of the wiring pattern is enhanced because the metallic film constituting through-hole land 112A extends to back face 110b of printed wiring board 110 through the sidewall constituting hole 111. However, when the soldering is performed to through-hole land 112A, a solder material moves easily into hole 111 because the metallic film is formed on the sidewall constituting hole 111. Therefore, the flux generated by the soldering cannot be prevented from extending onto back face 110b of the printed wiring board.
In the configuration of single-sided land 112B in FIG. 6B, the metallic film is not formed on the sidewall constituting hole 111, but an insulating material is exposed on the sidewall. When the soldering is performed to single-sided land 112B, the solder material remains in the metallic film formed on front face 110a of printed wiring board 110, and hardly moves to back face 110b of printed wiring board 110 through the sidewall constituting hole 111. Therefore, the flux hardly extends onto the side of back face 110b of printed wiring board 110. However, the peeling strength of the wiring pattern is weakened because the metallic film does not extend to back face 110b of printed wiring board 110 through the sidewall constituting hole 111.
In the case that the technology disclosed in Japanese Unexamined Patent Publication No. 2012-94681 is applied in order to enhance the peeling strength of the wiring pattern of printed wiring board 110, it is necessary to perform a process of holding the end portion of the land by the paint printed by the silkscreen. Therefore, unfortunately a production process becomes complicated.